A great many ingenious safety caps have been designed to prevent children's access to containers in which materials may be packaged which might injure the child if he had access thereto. Many of such caps have employed a special design of an inner cap and an outer cap which are so related, one to the other, that adults can, by following simple instructions, open the container, whereas a child, unable to read or understand instructions, cannot so open the container. The Poison Prevention Act of the U.S. has promulgated many such closures.
There has been a need, however, in the packaging and filling industry to have a simply applied overcap capable of use upon the standard metal screwcaps, which are in use extensively. The requirements of being able to machine-apply a cap to a standard metal screwcap and yet allow its subsequent use by adults to open and close the container has been present for some time. The present invention provides a simple, one-piece molded cap, which may be applied upon filling machinery by a simple downward straight-line motion applied to the container after it has received the standard metal screwcap closure. Once applied, the overcap will freewheel on the standard metal cap until pressure is applied to it in a prescribed manner to allow the overcap to operationally engage the standard metal cap for opening or closing motion.